In MCTS, what to do if I do not want to simulate till the end of the game?
Famous example is AlphaZero. It doesn't do unrolls, but consults the value network for leaf node evaluation. The paper has the details on how the update is performed afterwards:

The leaf $s'$ position is expanded and evaluated only once by the network to gene-rate both prior probabilities and evaluation, $(P(s′ , \cdot),V(s ′ )) = f_\theta(s′ )$. Each edge $(s, a)$ traversed in the simulation is updated to increment its visit count $N(s, a)$, and to update its action value to the mean evaluation over these simulations, $Q(s,a) = \frac{1}{N(s,a)}\sum_{s,a\to s'}V(s')$  , where $s, a\to s′$ indicates that a simulation eventually reached s′ after taking move a from position s.